The present invention relates to a method for determining the pose of an object, preferably of a hand-held medical device such as an ultrasound probe.
In various technical fields, it is of great importance to accurately determine the pose, i.e., the three-dimensional orientation and position, of an object while the object is being moved. For example, data acquired during ultrasound imaging may be improved if the pose of the ultrasound probe can be accurately determined during the process of acquiring the data. It has been suggested to determine the pose of such an ultrasound probe by means of optical tracking. For example, US 2004/0100557 A1 discloses a method for tracking the position and orientation of an ultrasound beam emitted from an ultrasound probe using, e.g., a three-dimensional video tracking system. According to this known method, the object to be tracked is provided with specific marker elements which are imaged by the video system. Analyzing the images taken by the video system allows for determining the three-dimensional position and orientation of the ultrasound probe as long as these markers are visible to the system.
However, during the process of imaging a patient by means of ultrasound, the user of the ultrasound device often has to perform complicated movements in order to properly image the patient. During these movements, one or even most of the markers on the ultrasound probe may be covered, e.g., by a hand of the user or the user in another way obstructs the field of view of the two cameras. While the markers are not fully visible to the video tracking system, the full pose information cannot be determined. The ultrasound image data taken during such a period of time may be of worse quality or even useless.